Why not feed wet food with fish in it?

I"m sure this has been addressed, but I did a search and got all kinds of things unrelated, so figured it was just easier to ask the question.

I'm trying to switch my furbabies over to canned food, and have been trying many different brands and types (pate, shredded, chunks, etc.), but so far the most popular BY FAR are the ones with fish, which is strange to me since their dry food has always been chicken and they have shunned the dry in fish flavors.

So...why is fish bad for them?

Also, Sven, our CRF kitty, will only lick up the gravy, and leaves the meat, so I figured that pate would be the ticket. When I got him pate and added water to make a big bowl of gravy, he wouldn't have anything to do with it, with several different flavors! Got any suggestions? I try cutting up any meat portions in the food into smaller pieces with a spoon, and if I"m lucky, he sucks up all the juice until the pieces left are practically bone dry, but I really want him to eat the actual meat, since I'm guessing that's where the real protein is. (I DO add extra water, too, to give him even more to lick up), then when all that's left is the dry meat, I add just a touch more water to that in case he wants to return later to suck THAT up.

So, this is really a two-fold question. What's wrong with fish, and is it normal for cats to just eat the liquid in canned food and leave the meat, especially when they are used to eating dry (and and still have dry available?

Fish is processed Whole.. unlike beef or lamb that are de boned completely ... chicken depending on brand usually is about 75% deboned

Since fish is processed in this manner it has a high ASH level .. Thus most with Uti prone cats will avoid it ... IMHO it should not be the main diet nor do I tend to buy all fish flavors unless I have a URI and need smelly...

Yes gravy is tasty and many cats do not understand re formed meat ... you may want to pop it in the blender to a more pate consistancy

I avoid fish flavored or mostly made up of fish canned...however if there is some in it lower down on the ingredient list like the fifth down or so then i might still buy it if it's not the main source of protein and there's small amounts. I read somewhere that the rule of thumb with cats and fish is that if it is a fish that eats other fish (tuna, salmon, etc.) it is not something you want to feed on a regular basis. However if it is a bottom dwelling type fish then it is at least better. I think it's because levels of magnesium or something, I can't remember the reasoning off hand. So I still won't buy flavors of "ocean whitefish" but say it is quite down there on the list of ingredients and the main protein is coming from something else then I won't completely rule it out.
I've just finished switching all three of my cats to canned and oddly enough even the more stubborn of them did not care for the fishy type foods I first offered him anyhow so we don't even bother in this house.

I avoid it because I have a chronic FLUTD boy. The last time I fed him a can of fish flavored food, he blocked and landed in the ER for 2 days. That was the most expensive can of cat food that I ever purchased.

My cat is the same way with the gravy. He just licks it up and leaves the meat. He doesn't go for many pate style foods, but his absolute favorite food is Whiskas Entrees. They're pate style in the plastic trays and he gobbles them up.

I've gotten him up to 1/2 wet/dry on it and I could probably get him to 100% wet on it, but I like the half and half idea.